Wind Tunnel Free

Turn your iPad/iPhone into a wind tunnel simulator !
Draw obstacles and watch the fluid flow around. Experiment with different sizes, shapes, aerodynamic profiles and see what happens !
Tap the blue button to bring application controls. Three segmented controls let you choose between:
• 4 touch actions:  interact with the fluid, draw walls, insert smoke probe, use eraser tool.
• 4 visualization modes:  particles, smoke, pressure field, velocity field.
• 2 simulation modes:  wind tunnel (with adjustable wind speed), free mode (with no constrained wind).

If you are interested in more options, check out Wind Tunnel, the paid version of this app, with many more features!
New in version 1.5.1:
- updated for iOS 9
New in version 1.5:
- improved retina graphics
- new simulation engine for dual-core devices
- iPhone 5 support
- other graphic improvements
New in version 1.3:
- Much more accurate fluid simulation engine.
- Visualization of velocity field, with this color scheme : black (fluid at rest), blue, red, yellow (highest speed).
- New preset models (try "swirl" !).
- Ability to change smoke color : in "interact" touch action and "smoke" mode, double tap on the smoke source, at the top of the screen
- Fixed bugs on boundary conditions.

New in version 1.2:
- Added support for older iphones and ipod touch (armv6)
- Minor bug fixes
- Added models of the "Lite" version

Fluid motion is computed by solving Navier-Stokes equations, at high definition ( 23000 grid cells on ipad ) thanks to a well-optimized code taking the most out of CPU performance.
Thank you all for your great comments.